We gradually reduce the land from its outlying borders

What does the Al-mighty’s saying mean: {See they not that We gradually reduce the land from its outlying borders? (Where) Allah commands there is none to put back His command: and He is swift in calling to account.}[1], and His Al-mighty’s saying: {..see they not that we gradually reduce the land (in their control) from its outlying borders? Is it then they who will win?}